1. Field of the Invention
The present invention relates to a resin sealing method and apparatus of effecting resin sealing after the pad of a semiconductor chip mounted on a substrate is joined to the electrode of the substrate through a bump. Particularly, the present invention relates to a resin sealing method and apparatus filling the gap between a semiconductor chip and a substrate with resin.
2. Description of the Background Art
In a semiconductor device having the pad of the semiconductor chip and the electrode of the substrate electrically connected via a bump, resin is inserted or filled into the gap between the semiconductor chip and the substrate and is then cured. This resin sealing is carried out in order to prevent generation of cracks at the junction due to thermal stress, and intrusion of a substance that adversely affects the semiconductor chip such as intrusion of impurities and moisture.
Conventionally, the method shown in FIGS. 5A-5D is employed in order to insert and cure resin in the gap between a semiconductor chip and a substrate. FIGS. 5A-5D are plan views of a semiconductor device corresponding to respective steps of a conventional resin sealing method.
Referring to FIG. 5A, liquid resin 102 is applied around a semiconductor chip 101 mounted on a substrate 100 so as to substantially surround the circumference thereof. A portion of the circumference of semiconductor chip 101 that is to serve as an outlet 103 is left absent of liquid resin 102.
Referring to FIG. 5B, the atmosphere around substrate 100 is reduced in pressure. Accordingly, the air present between substrate 100 and semiconductor chip 101 is output from outlet 103 as exhaust 104.
Referring to FIG. 5C, the viscosity of the applied liquid resin 102 is reduced by applying heat under the state where the atmosphere around substrate 100 is reduced in pressure. As a result, liquid resin 102 reduced in viscosity flows into the gap between substrate 100 and semiconductor chip 100 by the capillary action to be connected at the portion absent of the resin to become annular. Thus, the gap between substrate 100 and semiconductor chip 101 is filled with liquid resin 102 leaving a closed cavity 105 that is reduced in pressure.
Referring to FIG. 5D, the atmosphere around substrate. 100 is pressurized up to the atmospheric pressure. Under atmospheric pressure, closed cavity 105 in the gap between substrate 100 and semiconductor chip 101 is compressed by the pressure difference from the surrounding space to be eliminated. In other words, the entire region of the gap between substrate 100 and semiconductor chip 100 is filled with liquid resin 102. Then, heating is applied to cure liquid resin 102. By the foregoing steps, cured seal resin is formed at the gap between substrate 100 and semiconductor chip 100, and also at the circumference of semiconductor chip 101.
The conventional resin sealing method poses the following problems shown in FIGS. 6A-6D. FIGS. 6A-6D are plan views of a semiconductor device corresponding to respective steps of a conventional resin sealing method representing the problems. Referring to FIG. 6A, liquid resin 102 is applied on substrate 100, likewise FIG. 5A. In reducing the pressure of the atmosphere around substrate 100, there is the case where abnormal exhaust 106 penetrates through liquid resin 102 to be output from a region other than outlet 103 due to uneven application of liquid resin 102, as shown in FIG. 6B. Also, in pressurizing the atmosphere around substrate 100, there is the case where liquid resin 102 compressed towards closed cavity 105 by the pressure difference from the surrounding space is partially concentrated at the corner of semiconductor chip 101 to rise over the top surface of semiconductor chip 101. There is also the case where abnormal exhaust 106 is output from substantially the entire circumference of semiconductor chip 101 when the area of the cross section of outlet 103 is not large enough.
In the foregoing cases, a portion of liquid resin 102 will be blown off by the abnormal exhaust 106 to adhere on the top surface of semiconductor chip 101 as shown in FIG. 6C. The adhered liquid resin 102 will remain on the top surface of semiconductor substrate 101 as resin covering 107. This resin covering 107 is cured by the heating process as shown in FIG. 6D to cause appearance defect in the completed semiconductor device to degrade the yield.
In view of the foregoing, an object of the present invention is to provide a resin sealing method and apparatus to improve the yield by preventing generation of a resin covering in filling the gap between a substrate and a semiconductor chip with resin.
According to an aspect of the present invention, a resin sealing method achieving the above object has resin inserted and cured in the gap formed between a substrate and a semiconductor chip mounted on the substrate. The resin sealing method includes the steps of applying resin of a predetermined amount, which is set corresponding to the circumferential configuration of the semiconductor chip, at or along the circumference of the semiconductor chip under a state retaining a predetermined void or space between the resin and a side face of the semiconductor chip, reducing the pressure of the atmosphere around the substrate to exhaust air from the gap, reducing the viscosity of the applied resin to partially fill the gap with resin and thereby leaving a closed cavity reduced in pressure, and pressurizing the atmosphere around the substrate to compress the closed cavity from the surrounding atmosphere due to the pressure difference therebetween to entirely fill the gap with resin.
According to this resin sealing method, resin of a predetermined amount is applied at or along the circumference of the semiconductor chip in such a manner so as to retain a void or space between the resin and the side face of the semiconductor chip. Accordingly, a region absent of resin is formed surrounding the semiconductor chip at the substrate plane. By reducing the pressure of the atmosphere around the substrate, the air present between the substrate and the semiconductor chip is exhausted through the region where resin is not applied, i.e. through the gap or space formed between the resin applied at the circumferential position of the semiconductor chip and the side face of the semiconductor chip. Since this resin-free space forms a region where air can be exhausted having a large area of cross, section at the circumference of the semiconductor chip, exhaust can be effected stably.
At the corner of the semiconductor chip, the amount of resin to be applied is reduced or a region absent of applying resin is provided. As a result, exhaust can be effected in stability at the corner region where exhaust is concentrated so that the exhaust pressure is increased. Thus, there is the advantage superior in practical usage of providing a resin sealing method and apparatus that can prevent generation of a resin covering caused by abnormal exhaust and resin concentration.
In the above resin sealing method, the step of applying resin preferably has the amount of resin applied at the circumferential position of the site where the circumferential configuration of the semiconductor chip corresponds to a corner set lower than the amount of resin applied at the circumferential position of other sites of the semiconductor chip.
In a preferable embodiment of the resin sealing method of the present invention, the step of applying resin includes the step of applying resin of a predetermined amount at the circumferential position of the semiconductor chip excluding the site where the circumferential configuration of the semiconductor chip corresponds to a corner.
According to another aspect of the present invention, a resin sealing method of inserting and curing resin in a gap formed between a substrate and a semiconductor chip mounted on the substrate includes the steps of applying resin of a predetermined amount, which is set corresponding to the circumferential configuration of the semiconductor chip, at or along the circumference of the semiconductor chip in contact with a portion of the side face of the semiconductor chip at one region and retaining a predetermined void or space between the resin and another region of the side face, reducing the pressure of the atmosphere around the substrate to exhaust air from the gap, reducing the viscosity of the applied resin to partially fill the gap with resin and thereby leaving a closed cavity reduced in pressure, and pressurizing the atmosphere around the substrate to compress the closed cavity from the surrounding atmosphere due to the pressure difference therebetween to entirely fill the gap with resin.
In a preferable embodiment of the resin sealing method of the present invention, the step of exhausting includes the step of reducing the pressure of the atmosphere around the substrate from the atmospheric pressure down to a predetermined pressure over a predetermined period of time.
The resin sealing apparatus of the present invention fills a gap formed between a substrate and a semiconductor chip mounted on the substrate with resin. The resin sealing apparatus includes an application unit applying resin of a predetermined amount, which is set corresponding to the circumferential configuration of the semiconductor chip, at the circumference of the semiconductor chip in a manner retaining a predetermined void or space between the resin and the side face of the semiconductor chip, a pressure reduction unit to reduce the pressure of the atmosphere around the substrate to exhaust air from the gap, a viscosity reduction unit reducing the viscosity of the applied resin to partially fill the gap with resin leaving a closed cavity reduced in pressure, and a pressurization unit pressurizing the atmosphere around the substrate to compress the closed cavity from the surrounding atmosphere due to the pressure difference therebetween to entirely fill the gap with resin.
According to this resin sealing apparatus, resin of a predetermined amount is applied at the circumferential position of the semiconductor chip under a state retaining a void or space relative to the side face of the semiconductor chip. Accordingly, a region absent of resin is formed at the substrate plane, surrounding the circumference of the semiconductor chip. When the atmosphere around the substrate is reduced in pressure, the air present in the gap between the substrate and the semiconductor chip is exhausted through the region where resin is not applied, i.e. through the space formed between the resin applied at the circumferential position of the semiconductor chip and the side face of the semiconductor chip. Since the region from which air is exhausted is formed to have a large area of cross section at the circumference of the semiconductor chip, exhaust can be effected stably.
In a preferable embodiment of the resin sealing apparatus of the present invention, the atmosphere around the substrate is reduced in pressure from the atmospheric pressure down to a predetermined pressure over a predetermined period of time by the pressure reduction unit of the resin sealing apparatus.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.